With reference to FIG. 11, a contour shape measuring machine 10 consists of a horizontally feeding mechanism 13 which is provided on a column 12 standing on a base 11, and a detector 14 which has a probe 15 and is provided on the horizontally feeding mechanism 13 in such a manner as to freely move in a horizontal direction (X). The detector 14 detects the displacement of the probe 15 in a vertical direction (Z). A scale is built in the horizontally feeding mechanism 13, and the scale detects the horizontal movement amount of the detector 14.
When the detector 14 moves in the direction X while the probe 15 is in contact with a measured area on the workpiece 16, the detector 14 detects the vertical displacement of the probe 15, and the scale of the horizontally feeding mechanism 13 detects the horizontal movement amount of the detector 14. Thus, the contour shape of the workpiece 16 is measured.
Required as measured values are a geometric shape value (such as the diameter of a circle, the longer diameter and shorter diameter of an ellipse, and the central position of a circle, which are calculated by setting the shape data to a geometric shape such as a straight line, a circle and an ellipse), and a geometric shape boundary value (such as a position of a boundary where two geometric shapes intersect each other, an angle formed by two geometric shapes which intersect each other, and the distance between boundaries).
An example of the data processing unit is provided with either a system which describes a shape view (which plots values at each measurement point in X and Z directions) by outputting the shape data directly to an X-Y plotter, or a system which has a data processing unit and displays a shape view on a CRT, or both of these two systems. According to the system which outputs the shape data to the X-Y plotter, an operator must read the geometric shape value and the geometric shape boundary value on the shape view. According to the system which has the data processing unit, the data processing unit is capable of calculating the geometric shape value and the geometric shape boundary value as explained below with reference to a flow chart of FIG. 9 and a view of FIG. 10.
First, when the operator measures the workpiece 16 by the contour shape measuring machine 10 (step 121), the CRT displays a shape view which describes measured positions (step 122). FIG. 10 shows the outline of an example in which a screw-like triangular workpiece is measured. The reference numeral 141 is a measurement starting point, and 151 is a measurement ending point.
With reference to the shape view being displayed, the operator determines and designates applicable geometric shapes (all of which are straight lines in this example.) The operator also specifies an objective area of the geometric shape value calculation (step 124). Large measurement errors normally in the vicinities of the measurement starting point 141 and the measurement ending point 150, and in an area where the shape changes greatly. An area except for those areas (e.g. an area between a point 142 and a point 143 in FIG. 10) is designated as the objective area of the geometric shape value calculation. On designation of the objective area of the geometric shape value calculation, the shape data in the designated area is calculated automatically in accordance with the designated geometric shapes (step 125), and the geometric value (a straight line Lh in the case of the area between the point 142 and the point 143) is displayed (step 126).
Then, the operator determines whether to calculate a geometric shape value in the next area of the shape view or a geometric shape boundary value (step 127). To calculate the geometric shape value in the next area, the process returns to the step 123, and the operator determines and designates the applicable geometric shape and designates areas such as "an area between a point 144 and a point 145", "an area between a point 146 and a point 147", and "an area between a point 148 and a point 149." Thereby, the geometric shape values of the straight lines Li, Lj, Lk, etc. are calculated.
To calculate the geometric shape boundary value, the operator designates two geometric shapes such as the straight lines Lh and Li (step 129). A geometric shape boundary value (coordinate values at an intersection 151 and an angle of intersection .theta.d) of the designate geometric shapes is automatically calculated (step 130), and the calculating results are displayed (step 131). Likewise, coordinate values at an intersection 152 and an angle of intersection .theta.e are calculated on designation of the straight lines Li and Lj. Coordinate values at an intersection 153 and an angle of intersection .theta.f are calculated on designation of the straight lines Lj and Lk.
Thereafter, the operator returns to the step 123 in order to calculate a geometric shape value in the next area, and returns to the step 128 in order to calculate a next geometric shape boundary value (step 132).
In order to find the geometric shape value, the operator must determine and designate the type of the geometric shape corresponding to the displayed shape. The operator must also designate the objective area of the geometric shape value calculation. Likewise, in order to find the geometric shape boundary value, the operator must separately designate two geometric shapes. It takes a long time to complete such a complex operation.
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of an automatic shape calculating method and apparatus for a contour shape measuring machine, the method and apparatus which automatically calculate a geometric shape value and a geometric shape boundary value in accordance with shape data without the operator's determining geometric shapes, designating objective areas of the geometric shape value calculation and designating the applicable geometric shapes of geometric shape boundaries.